Hip pads, and other protective padding, have been used for protecting the human body from damage due to impact from falls, accidents, sports, and other related events. In particular, bone fracture as a result of accidental falling is a common occurrence with elderly people, with people who have a osteoporosis, and people who are unsteady on their feet and have difficulty in walking. In elderly people, especially those with osteoporosis, bone fractures are very difficult to repair, and it is highly desirable to prevent them from occurring in the first place.
A variety of protective padding and garments have been made available in the past, but all with some shortcomings. A typical piece of protective wear is a pad that is either permanently fixed to a garment, or that slips into a pocket in the garment, or held in place by straps or a skin-safe adhesive so that the pad is positioned over a damage-prone area of the body. Such a damage-prone area, especially in the elderly, is the hip area. Hip fracture, which occurs in 2 to 3% of cases involving elderly fallers, generally involves fracture of the proximal end of the femur. This part of the femur consists of a head, neck, greater trochanter, and lesser trochanter. The greater trochanter projects outward at the most lateral area of the hip region and, being so located, is subjected to the brunt of impact force arising from a fall, in particular a sideways fall, onto the hip.
To protect the hip area, pads are typically fixed to the inside of clothing in the area that covers the hips, or are placed in pockets made in the clothing at the hip area. More specifically, the pads are typically positioned such that they overlie the greater trochanter, or, in the case of certain types of force or energy shunting pads, surround the greater trochanter without actually covering it.
The degree to which a pad needs to attenuate the force of impact during a fall is subject to much debate. This is because measurements of the force needed to fracture elderly cadaveric femurs in simulated fall loading configurations vary widely. These measurements range from 2110 Newtons (J. C. Lotz & W. C. Hayes, J. Bone Joint Surg. [Am], Vol. 72, pp 689-700, 1990) to 6020 Newtons (T. G. Weber, K. H. Yang, R. Woo, R. H. Fitzgerald, ASME Adv. Bioeng. BED22: pp 111-114, 1992) depending upon the rate of loading. In addition, the velocity at which a falling human torso impacts a hard surface such as a tile floor can vary from about 2.0 to about 4.5 meters/second. Average velocities of about 2.6 meters/second have been cited by researchers (S. N. Robinovitch, J. Biomech. Eng. Vol. 9, pp 1391-1396, 1994) who have measured the speed of human volunteers falling on their hips. Estimates of the force delivered to an unpadded greater trochanter during a fall also range widely from about 5700 Newtons to 10,400 Newtons (J. Parkkari et al., J. Bone and Mineral Res., Vol. 10, No. 10, pp 1437-1442, 1995).
The best evidence of pad effectiveness is obtained from clinical studies on living people. Such a study has been carried out by Lauritzen et al. (Lancet, Vol. 341, pp 11-13, 1993) using a hard shell-type pad. This pad was found to reduce incidence of hip fractures by about 50% in the population studied. In spite of these strong clinical results, the Lauritzen pad has been shown to provide relatively low force attenuation results when mounted on a surrogate hip and impacted by a heavy (35 kilogram) pendulum moving at a velocity of 2.6 meters/second (S. N. Robinovitch, et al., J. Biomechanical Engineering, Vol. 117, pp 409-413, 1995). Under these in-vitro test conditions, the Lauritzen pad reduced peak femoral force from about 5770 Newtons to about 4800 Newtons or only about 17%. A hip protector product based on the Lauritzen pad has been commercialized in Denmark by Sahvatex (a joint venture between Sahva A/S and Tytex A/S) under the tradename SAFEHIP.TM.. The hip protectors, which are oval-shaped structures containing plastic hard shells, are sewn into a pair of cotton underwear.
These clinical findings suggest two hypotheses. First is that the pendulum impact tests used by other investigators may not correlate well with pad performance in-vivo even though such tests may be useful in measuring the force reduction capabilities of various padding systems relative to one another. In such tests the pad is mounted on a surrogate hip which is held in a fixed position and struck laterally by a swinging mass weighing 35 kilograms or more. In an actual fall, the dynamics are somewhat different. In a fall, both the pad and human body mass are moving downward, in fact being accelerated downward due to gravity, and strike a fixed object such as the ground or a hard floor which does not move much in response. One would suspect that if an instrumented surrogate hip was dropped onto a hard surface, to better replicate fall dynamics, the rank ordering of various padding systems would probably be similar, but somewhat different percent force reduction results might be obtained. The second hypothesis assumes the pendulum test does correlate with in-vivo pad performance, and that even pads which provide relatively low levels of peak force reduction in-vitro (about 20% or so) can be effective in reducing hip fractures across a segment of the elderly population prone to falling. In either case, and regardless of test method, a pad which reduces peak force more than the clinically tested Lauritzen/Sahvatex pad should be even more effective in preventing hip fracture and protect an even broader segment of the elderly population.
Obviously, the more force reduction one obtains from a pad, the more likely it should reduce the incidence of hip fracture. However, our consumer research has taught us that, in addition to reducing the impact force exerted on the greater trochanter during a fall, pads must also provide other benefits to reinforce wearer compliance. These are related to both appearance and wearer comfort and include attributes such as maximum thickness, thickness profile, weight, breathability, flexibility, and conformability to the body, Prior pads have had many shortcomings in these areas.
Some prior art padding has been bulky and cumbersome in an attempt to provide for adequate protection from impact; many typical prior art pads purported to provide effective impact resistance are greater than 25.4 mm (1 inch) in thickness. Thin prior art pads typically provide low resistance from impact, characterized by less than about 30% peak force reduction as measured on surrogate hips either dropped or struck with heavy pendulums. Other padding has not been breathable, resulting in heat buildup on the skin that is covered by the pad. Still other padding has been stiff and rigid, thereby not conforming to the covered body parts. In addition, hard shell pads tend to be uncomfortable to sit on or sleep on when worn. Soft foam pads require greater thickness to absorb impact forces; the greater thickness results in a bulkier, less comfortable pad, and increased heat build up under the pad. All have resulted in relative discomfort to the users.
Our consumer research has shown that potential wearers, regardless of age or physical condition, are concerned with their appearance. Preferred are hip pads no thicker than about 25.4 mm (one inch), and more preferred are those about 19 mm (3/4 inch) maximum thickness or less. Thickness profile is also important. Preferred are pads which are tapered from the area of maximum thickness to the perimeter such that neither the pad nor the pad edges show under normal clothing. A perimeter thickness range around the pad of 12.77 mm (1/2 inch) or less is generally preferred. Even more preferred is a perimeter thickness range of 6.35 mm (1/4 inch) or less. Still even more preferred is a perimeter thickness range of 3.18 mm (1/8 inch) or less.
Since most potential wearers are elderly women of slender body habitus and low body mass, pad weight is a concern. Preferred are pads less than about 300 grams each (600 grams per pair). Even more preferred are pads which weigh less than about 200 grams each (400 grams per pair). Most preferred are pads which weigh less than about 100 grams each (200 grams per pair).
Unlike sports pads which are meant to be worn over very short periods of time, protective hip pads for the elderly are intended to be worn all day, indoors and outdoors, in all climates hot and cold, and across all humidity conditions. Typical foam pads are made from closed cell foams which do not pass moisture or perspiration from the body. In addition, such pads are thermal insulators and do not dissipate body heat effectively. This leads to even more perspiration and moisture buildup under the pad which can damage the skin of elderly wearers. Preferred pads thus have substantial open area, preferably at least about 5% or more, and more preferably about 10% or more, to permit evaporation of perspiration and to vent body heat.
Disclosed herein is a new, improved protective padding, that provides increased impact resistance in a relatively thin, lightweight pad. Increased impact resistance is maintained while providing breathability to prevent heat buildup and the associated discomfort. Additionally, this new pad provides for flexibility and conformance to the part of the human body being protected without any adverse impact on its protective qualities.